Robin Williams, the iconic comedian, film and television star who died at his California home this week, was battling the early stages of Parkinson's Disease, his wife has revealed.

Susan Schneider issued a statement through Williams' publicist, revealing that Williams, who was 63, had also been struggling with depression and anxiety.

Schneider said Williams had been "not yet ready to share publicly" his battle with Parkinson's Disease.

Parkinson's Disease is a degenerative disorder of the central nervous system.

The actor Michael J. Fox, who was diagnosed in 1991 with the disease, did not go public with the news of his own diagnosis for seven years.

Schneider also noted that Williams, who had battled with alcohol and drug addiction in his life, was sober at the time of his death.

Robin Williams

Williams' family have taken "some solace" in the extraordinary and emotional reaction to his death, Schneider said.

In her statement she referred to the "tremendous outpouring of affection and admiration for him from the millions of people whose lives he touched".

Schneider has requested that the full text of her statement be published.

This is the statement:

Robin spent so much of his life helping others. Whether he was entertaining millions on stage, film or television, our troops on the frontlines, or comforting a sick child - Robin wanted us to laugh and to feel less afraid.

Since his passing, all of us who loved Robin have found some solace in the tremendous outpouring of affection and admiration for him from the millions of people whose lives he touched. His greatest legacy, besides his three children, is the joy and happiness he offered to others, particularly to those fighting personal battles.

Robin's sobriety was intact and he was brave as he struggled with his own battles of depression, anxiety as well as early stages of Parkinson's Disease, which he was not yet ready to share publicly.

It is our hope in the wake of Robin’s tragic passing, that others will find the strength to seek the care and support they need to treat whatever battles they are facing so they may feel less afraid.

Williams' family have not announced funeral plans for the Oscar winner.

It is understood a private family service is planned, attended by close friends and family only.

Support is available for those who may be distressed by phoning Lifeline 13 11 14; Mensline 1300 789 978; Kids Helpline 1800 551 800.